Icaphoca choristodon n. gen., n. sp., described in the present study, represents the sixth monachine seal from the Neogene Pisco Formation of Peru. The species is solely known from the holotype, including a cranium with both mandibles, as well as five cervical vertebrae including the atlas and axis. This holotype was collected at the Cerro La Bruja locality, the type locality of Magophoca brevirostris, in the Ica Desert after which Icaphoca has been named. Stratigraphically, the holotype was recovered from strata underlying those of the Cerro La Bruja level (CLB level), from which Magophoca was recovered. These beds likely correspond with the P1-2 unit of the P1 sequence within the Pisco Formation. Assumed to be as old as 9 Ma (middle Tortonian), Icaphoca may be the oldest described monachine seal from the southeast Pacific. Following Magophoca and Noriphoca, Icaphoca is the third extinct monachine seal known to have six upper incisors. This plesiomorphic character is absent in all other extant and extinct Monachinae which have only four upper incisors. The elongation of the snout, as well as the presence of profound diastemas between the postcanine teeth, suggests that Icaphoca is closely related to Acrophoca from the upper Tortonian and Messinian of the Pisco Formation in the Sacaco area (Arequipa Department), c. 200 km southeast to Cerro La Bruja. The specific name choristodon refers to this spacing between the post-canine teeth. The close phylogenetic relationship between Icaphoca and Acrophoca is confirmed by the phylogenetic analysis, which retrieves both genera as sister taxa.
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RBINS Staff Publications 2025
Background: Lake Tanganyika is the world’s second deepest lake. Its diverse cichlid assemblage offers a unique opportunity for studying a deep-water host-parasite model in freshwater. Low host specificity and a broad host range including representatives of the Bathybatini tribe in the only monogenean parasite described from this habitat, Cichlidogyrus casuarinus Pariselle, Muterezi Bukinga & Vanhove, 2015 suggest a link between lower specificity and lower host density. Conversely, high host specificity and species richness are reported for monogeneans of the lake’s littoral cichlids. We further investigated whether the deep-water environment in Lake Tanganyika is really monogenean species-depauperate by investigating the monogenean fauna of Trematocara unimaculatum (a representative of the tribe Trematocarini, the sister lineage of the Bathybatini) and Benthochromis horii, a member of the tribe Benthochromini, found in the same deep-water habitat as the already known hosts of C. casuarinus. Methods: Sclerotised structures of the collected monogenean individuals were characterised morphologically using light microscopy and morphometrics. Results: Both examined cichlid species are infected by a single monogenean species each, which are new to science. They are described as Cichlidogyrus brunnensis n. sp., infecting T. unimaculatum, and Cichlidogyrus attenboroughi n. sp., parasitising on B. horii. Diagnostic characteristics include the distal bifurcation of the accessory piece in C. brunnensis n. sp. and the combination of long auricles and no heel in C. attenboroughi n. sp. In addition C. brunnensis n. sp. does not resemble C. casuarinus, the only species of Cichlidogyrus thus far reported from the Bathybatini. Also Cichlidogyrus attenboroughi n. sp. does not resemble any of the monogenean species documented from the pelagic zone of the lake and is among the few described species of Cichlidogyrus without heel. Conclusions: As two new and non-resembling Cichlidogyrus species are described from T. unimaculatum and B. horii, colonisation of the deep-water habitat by more than one morphotype of Cichlidogyrus is evident. Based on morphological comparisons with previously described monogenean species, parasite transfers with the littoral zone are possible. Therefore, parasites of pelagic cichlids in the lake do not seem to only mirror host phylogeny and the evolutionary history of this host-parasite system merits further attention.
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RBINS Staff Publications 2016
